Which fluid for Transmission?

[Lin]

I know this has been gone through before, but I have a specific purpose for reviewing it.  I currently have an MT647.  It is running fine but has a significant leak in around where it connects to the engine.  Since it seems to me that it can not be fixed without removing the engine/trans from the bus, which I do not want to do, I am looking for a thicker fluid in the hope of slowing the leak a bit.  I think I remember people saying they have used 30wt motor oil instead of transmission fluid.  Does anyone have specific experience with that?

[wg4t50]

I did that #30 wt oil in a 55 Chevy Power Glide, did fine for a while but let me sit when it pushed the seal out where the torque converter slid into the Power Glide, dumped the oil and I was in need of a tow.  That was 1960 when on liberty as a Jarhead 72 hr pass.
I would fix it while you have better choices.
Dave M

[Dave5Cs]

Lin I had one and just tightened the bolts and it pretty much sealed it up.

[TomC]

The leak will only get worse-get it fixed properly. Good Luck, TomC

[gus]

I'm having the same problem with my V730, 2 qts leak overnight!!

I'm thinking but haven't come up with a solution yet.

[AndyG]

Automatic transmissions do not like "substitute" fluids.  ATF is not simply a light weight oil.  It has different additives to help it lubricate as well as help the clutch plates grip properly.  Auto transmissions are also complex hydraulic systems which rely on the viscosity of the fluid to work correctly.  I think that most Allisons use Dexron fluid so stick with that.  As unpleasant as it sounds, you need to do a little investigating.  Get under the coach and clean things up to identify where the fluid is actually coming from.  Maybe you will get lucky and discover that it is only a lose plug/bolt/hose.

[luvrbus]

The HT 600 and 700 series can use about any type oil  the 15/40 is a common oil used and it is approved for Allison but I think the heavier the oil it is going to make the leak worse in time but give the 15/40 a shot it may work for you   

[Lin]

Thanks- I will look again to see if there is something that I can tighten to help.  I did show it to an independent transmission mechanic yesterday who said that one would have to get the engine separated from the transmission to fix whatever is leaking.  However, I was not to impressed with his knowledge.

It took me a long time to figure where the fluid was leaking because there were never significant amounts of oil on or under the bus.  When I noticed that it seemed moist around the plug on the housing between the engine and transmission, I removed the plug and the fluid poured out.  I did not see any way to get at what would be inside, but maybe there is.

Clifford, with regard to using 15/40 oil-- could the change over be done gradually by adding quarts as needed or would I have to change it all at once?

[robertglines1]

When you check your transmission is your dipstick always in all the way or is it pushed out??Are you checking it hot with engine running or cold??  you prob are doing right but others reading might not know answers.

[Lin]

Thanks Bob, but the engine is running and hot, on reasonably level ground, using the whole transmission dipstick.

Do you think that making the dipstick longer could be a temporary fix?

[luvrbus]

Lin, your problem is going to get worse and leave you the road when it goes,you are close to United Transmission Exchange have them check it for you,small leaks on Allison's turn into gushers in time fwiw 

Allison sells the kit with the pump gasket,seal,0-rings and the washers the kit is cheap the labor is not so cheap neither is the snap ring fixture I paid 385 bucks for one to install a $15.00 seal ouch!!!! maybe this spring I can find some time and help you,when you guys install the lockup for the torque converter for jakes sooner or later one is going to pay the price BTDT


good luck

[Lin]

Thanks for the reality check. I should really get a handle on the cost of the fix.  United Transmission is in San Bernardino-- about 2 hours at bus speeds.  Incidentally, this problem predates the Jake lockup project.  I've actually had it from the very beginning when the transmission was installed almost three years ago.

[luvrbus]

Was that a rebuilt or a take out Don installed in your bus ?

[robertglines1]

Lin; Just have to remind myself sometimes we have new readers that  need a little background and overfill transmissions and engines doing more harm than good..  Did'nt think about a longer dipstick---good one!   had a filter (spin on) gasket start leaking on a 750 thought I was in for a major!! got lucky and changed filter..  got lucky!!   

[Lin]

It was a rebuilt from Az/Global.